After his adventures in King Solomon's Mines, the fearless explorer Allan Quatermain is once again drawn into a perilous journey when he decides to find his missing brother Robeson, who had set out in search of a lost city filled with untold riches. Accompanied by his fiancée Jesse Huston, an equally intrepid archaeologist, and their warrior friend Umslopogaas, Quatermain embarks on a quest that takes them deep into the heart of Africa. Their journey is fraught with dangers, from treacherous landscapes to hostile tribes guarding their secrets, all the while driven by the hope of finding Robeson and the mythical city of gold.

As the group ventures further into uncharted territories, they encounter a variety of remarkable characters, including a flamboyant, Swahili-speaking warrior played by James Earl Jones, and face challenges that test their courage and resolve. Their quest leads them to discover a mysterious lost city, hidden from the world for centuries, where they uncover secrets beyond their wildest imaginations. Meanwhile, they must also contend with unscrupulous rivals who seek the city's riches for their own selfish gains, setting the stage for conflict and adventure as they navigate the complex politics and cultural landscapes of this hidden civilization.